Further experimental studies of two-body radiative ${\rm Y}$ decays

Continuing our studies of radiative ${\rm Y}$ decays, we report on a search for $\overrightarrow{{\rm Y}}\gamma \eta$ and $\overrightarrow{{\rm Y}}\gamma f_J\mathrm{}\left(2220\right)\mathrm{}$ in $61.3$ ${\mathrm{pb}}^{-1}$ of $e^{+}{e}^{-}$ data taken with the CLEO II detector at the Cornell Electron Storage Ring. For the $\gamma \eta$ search the three decays of the $\eta$ meson to ${\pi }^{+}{\pi }^{-}{\pi }^0,$ ${\pi }^0{\pi }^0{\pi }^0$, and $\gamma \gamma$ were investigated. We found no candidate events in the $(3\mathrm{}\pi {)}^0$ modes and no significant excess over expected backgrounds in the $\gamma \gamma$ mode to set a limit on the branching fraction of $\mathcal{B}\left(\overrightarrow{{\rm Y}}\gamma \eta \right)<\mathrm{}2.1\mathrm{}\times {10}^{-5}$ at $90\%$ C.L. The three charged two-body final states $h\overline{h}(h={\pi }^{+}{,K}^{+},p)$ were investigated for $f_J\mathrm{}\left(2220\right)\mathrm{}$ production, with one, one, and two events found, respectively. Limits at $90\%$ C.L. of $\mathcal{B}\left(\overrightarrow{{\rm Y}}\gamma f_J\right)\times \mathcal{B}{(f}_J\to h\overline{h})\sim 1.5\times {10}^{-5}$ have been set for each of these modes. We compare our results to measurements of other radiative ${\rm Y}$ decays, to measurements of radiative $J/\psi$ decays, and to theoretical predictions.